DETROIT (AP) _ General Motors Corp. has reached an agreement with East Germany's state- owned automaker to jointly build Opel cars.

The agreement signed Sunday by GM's West German subsidiary, Adam Opel AG, and Automobilwerk Eisenach represents GM's second move into Eastern Europe in recent months. GM earlier agreed to a $150 million joint venture in Hungary.

Opel, based in Ruesselsheim near Frankfurt, and Automobilwerk Eisenach said they hope to produce 150,000 Opels yearly at the East German company's plant in Eisenach near the West German border.

The cars will be marketed in East Germany, GM spokesman Jack Harned said Sunday.

''This has a lot to do with the unification of Germany,'' Harned said. ''We have a good presence in Europe. Now we'll have more of a presence in Eastern Europe. It's a very important move for GM.''

GM, the world's biggest automaker, did not disclose size of its stake or its partner's in the venture. Details were to be released later today.

GM's venture to build vehicles with RABA, Hungary's state-owned manufacturer of trucks, diesel engines and axles, made GM the first U.S. automaker to invest in Eastern Europe since its political and economic liberalization.

Ford Motor Co. says it is watching the Eastern European market. Chrysler Corp. sells cars in Europe but has no independent manufacturing plants there.